Sealed magnetic switch and method of manufacture



Mam}! 1966 w. ANDERSON ETAL 3,240,897

SEALED MAGNETIC SWITCH AND METHOD OF MANUFACTURE Filed June 19, 1964 )WEMToEs LESTER W AdoEzsoyd Am: HARRY CHANOWITZ 'Mmwm, KolkMw wru,

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United States Patent C) SEALED MAGNETIC SWITCH AND METHOD OF MANUFACTURE Lester W. Anderson, Lombard, and Harry Chanowitz,

Slrokie, IlL, assignors to C. P. Clare & Company, Chicago, Ill., a corporation of Delaware Filed June 19, 1964, Ser. No. 376,510 5 Claims. (Cl. 200--87) This invention relates to sealed magnetic switches, and, more particularly, to sealed magnetic switches of the type having new and improved means for damping movement of a magnetic element included in the switch, as well as a method of manufacturing such a switch.

Many of the applications or circuits in which it is desirable to use sealed magnetic switches are such that it is necessary or at least desirable to prevent oscillation of the free and overlapped ends of the magnetic elements or reeds when the switch is released. The copending application of John Kutyla, Serial No. 319,457, filed October 28, 1963, and of Harry Chanowitz, Serial No. 319,383, filed October 28, 1963, both of which applications are assigned to the same assignee as the present application, disclose sealed magnetic switches in which depressions are formed in the glass housing of the switch units in positions directly opposite the outer surfaces of the uniplanar free ends of the reeds and adjacent the gap normally provided therebetween. When the switch is released by the removal of the holding or operating field, the overlapped and previously engaged ends of the magnetic elements are separated by their inherent resilience, and the ends strike the depressions to damp their kinetic energy. This prevents any oscillation that might result in false operation of the switch.

The Chanowitz application discloses an apparatus for and a method of forming the damping depressions or projections in which the flames of a pair of torches are directed at the glass housing of the switch in the areas in which the depressions are to be formed so as to soften the glass in these regions. The pressure of the flame together with the partial vacuum present within the sealed envelope displaces the softened glass inwardly until it engages the planar surfaces of the two reeds. Although the softened glass tends to cool and thus solidify because of the removal of heat through the metal of the engaged reeds, it has been determined that some deflection of the reeds can occur. Because the sealed switches are checked for proper operating characteristics before the dimpling or depression forming operation, excessive displacement of the reeds toward each other in the gap area tends to change the operating characteristics or sensitivity of the switch by reducing the operating current. It has been the practice to select switches for dimpling that have operating currents that are high in the acceptable range so that any reduction in the operating current occasioned by excessive gap reduction due to the depression forming operation would not reduce the operating current sensitivity below the minimum acceptable value. This problem of variations in the gap setting is particularly acute in switches in which the reeds or magnetic members are not concentrically disposed within the glass housing.

Further, in the apparatus shown in the Chanowitz application, the switches are located relative to the flames of the torches by using gauges or fixtures bearing against the planar surfaces of the outer or terminal portions of the reeds. Since the reeds are angled slightly relative to the elongated glass housing in the normal construction of the switch, it is possible to achieve only nominal control of the spacing between the glass and the two flames.

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Accordingly, one object of the present invention is to provide a new and improved sealed magnetic switch unit.

Another object is to provide a sealed magnetic switch unit including new and improved damping means.

Another object is to provide a sealed magnetic switch including damping means in which the damping means do not change the operating characteristics of the switch.

A further object is to provide a sealed switch in which damping means provided therein are accurately located relative to the engaged portions of the magnetic elements in even those switches in which the magnetic elements are not concentrically disposed relative to the glass housing or envelope.

Another object is to provide a sealed magnetic switch unit having damping means that engage the edges of the reeds rather than the planar surfaces thereof.

A further object is to provide a sealed magnetic switch including damping depressions or projections offset approximately 45 from the planar surfaces of the overlapped gap defining ends of the magnetic elements or reeds.

A further object is to provide a new and improved method of forming damping depressions or projections in the envelope of a sealed switch, which method is capable of compensating for eccentricities in the location of the magnetic elements relative to the housing of the switch.

Another object is to provide a method of making sealed magnetic switch units in which the glass housing of the sealed switch is softened at points offset approximately 45 from the planes of the gap defining inner ends of the reeds so as to form damping depressions or projections engaging the reeds along their edges rather than along their planar surfaces.

In accordance with these and many other objects, an embodiment of the invention comprises a sealed magnetic switch having an elongated glass envelope or housing in the opposite ends of which a pair of magnetic reeds are sealed with their uniplanar inner ends disposed in an overlapped and spaced position defining a gap. To provide means for damping or preventing oscillation of the gap defining ends of the magnetic reeds when the switch is released, the walls of the housing are provided with depressions offset approximately 45 from the planes of the ends to engage the overlapped ends of the reeds along their edges rather than along their planar surfaces. The engagement of the end portions of the reeds along the edges removes sufiicient kinetic energy from these reeds when the switch is released. This engagement along the edges results in the application of at least a portion of the forces along the transverse dimension of the reeds when the end portions are engaged by the softened glass during the dimple forming operation so as to prevent excessive deflection of these reeds and a consequent change in the operating characteristics of the switch during the depression forming or dimpling operation.

The damping projections or depressions are formed in the housing by applying heat to generally opposed regions on the glass housing along lines offset approximately 45 from the planes of the reeds to be engaged. The application of heat is terminated after the glass becomes sutficiently softened to be displaced inwardly by the partial vacuum within the envelope and the pressure of the flame to engage one edge of the adjacent reed. The softened glass may be formed about one or both of the mutually perpendicular walls defining the edge. The termination of the heating coupled with the removal of heat through the metal of the engaged reed and the cooling of the glass in the atmosphere solidifies the glass in a position engaging the reed. Since the softened glass engages the reed along its edge, at least a portion of the force of the moving glass is applied transverse to the length of the reed in a direction in which the reed is not capable of being deflected. This reduces the component of force applied to the planar surface of the reed to such an extent that the preset gap between the overlapped ends of the two reeds is not materially altered, and the previously checked operating sensitivity of the switch is not varied. In addition, by applying heat in positions offset from the planar surfaces of the reed, the edge surfaces rather than the planar surfaces of the outer terminal portion of the reed can be used for positioning the reed relative to the heat source, such as a pair of torches, and any lack of concentricity between the two reeds and the envelope is automatically compensated. In other words, the use of the edge surfaces of the terminal portions of the reeds automatically varies the distance of the glass envelope with respect to the torches in eccentric switches to form depressions or projections of different heights and avoids the production loss previously encountered in attempting to dimple eccentric switches.

Many other objects and advantages of the present invention will become apparent from considering the following detailed description in conjunction with the drawings in which:

FIG. 1 is a plan view in partial section of a sealed magnetic switch unit embodying the present invention;

FIG. 2 is an enlarged sectional view taken along line 22 in FIG. 1 shown in combination with a pair of torch means used to form damping depressions in the switch;

FIG. 3 is a sectional view taken along line 3-3 in FIG. 2;

FIG. 4 is a sectional view taken along line 4-4 in FIG. 2', and

FIG. 5 is a sectional view similar to FIG. 2 illustrating another embodiment of the switch and method of making the switch.

Referring now more specifically to FIG. 1 of the drawings, there is illustrated a sealed magnetic switch It) which embodies the present invention and which includes an elongated glass or dielectric housing or envelope 12 in the opposite ends of which a pair of magnetic reeds 14 and 16 are sealed with their inner ends disposed in an overlapped and spaced position to define a gap 18. Each of the reeds 14 and 16 includes a generally cylindrical intermediate portion 14a and 16a that is sealed in the ends of the glass housing 12 and a flattened outer end or terminal portion 14b and 16b. The overlapped or gap defining ends of the magnetic elements 14 and 16 comprise generally uniplanar portions 140 and 160 preferably provided with a layer of contact material, such as gold, along their mating surfaces. The switches can be made by any suitable method. These methods of making the switch 10 are such that a partial vacuum results within the interior of the sealed housing 12.

To provide means for preventing oscillation or flagging of the overlapped end portions 140 and 160 of the magnetic reeds 14 and 16 when the switch 10 is released, the housing 12 is provided with a pair of damping projections or depressions 2t) and 22 which engage the end portions 14c and 16c, respectively, immediately adjacent the portions thereof defining the gap 18. The depressions 20 and 22, which are formed integral with the glass of the housing 12, are each disposed generally on a line passing through the planar surface of the engaged one of the magnetic terminals at an angle of around In other Words, a center line passing through the depression 20 intersects the uniplanar end portion 14c at an angle around 45, and a center line passing through the depression 22 intersects the plane of the end portion 16c of the terminal 16 at an angle around 45. As illustrated in FIG. 2, the depression 20 includes a right angle or somewhat L-shaped recess 20a in which one edge of the inner end portion 140 of the magnetic reed 14 is received, and the depression 22 includes a similar recess 22a in which an opposite edge of the end portion 16c of the magnetic reed 16 is received. The recesses 20:: and 22a are shown as comprising L-shaped recesses, but this configuration is determined by the configuration of the engaged edge portion of the magnetic terminals 14 and 16 and could be of many other configurations in dependence on the shape of the end portions 14c and 160.

The switch 19 is operated by applying a magnetic field to the elements 14 and 16 so that the overlapped end portions 14c and 160 defining the gap 18 are moved into engagement. The value of current through an operating winding that is required to move the overlapped ends and into engagement is, to a large degree, dependent on the characteristics and size of the gap 18 between these end portions and comprises the operate characteristic or sensitivity of the switch. In manufacturing the switches 10, this operate sensitivity is held Within a predetermined range of values. When the switch 10 is released by removing the applied magnetic field, either the initial operating field or a smaller holding field, the inherent resilience of the magnetic elements 14 and 16 causes the separation of the overlapped end portions 14c and 160 and imparts kinetic energy thereto. This energy has a tendency to cause the end portions 14c and 160 to oscillate about their normal positions with the result that, in some instances, the immediate reapplication of a holding or operating signal can cause reclosure of the end portions 140 and 160 and a consequent false operation of the switch It). This oscillation or flagging of the magnetic elements 14 and 16 is prevented by the damping projections or depressions 20 and 22. As the end portions 14c and 160 separate and move away from each other, they are received within the recesses 20a and 22a and engage the depressions 20 and 22 so that their kinetic energy is damped or absorbed. This prevents oscillation of the reeds and consequent reclosure of the switch 10. In switches manufactured in accordance with the present invention, it has been determined that the engagement of the overlapped end portions 140 and 16c along opposite edges thereof by the depressions 20 and 22 is effective to damp or absorb the kinetic energy and prevent oscillation fully as effectively as in prior constructions in which the depressions are so formed as to engage the planar surfaces of the end portions 140 and 16c.

The damping depressions or projections 20 and 22 can be formed in the glass housing 12 of the sealed switch 10 using the techniques and apparatus disclosed and described in detail in the above-identified copending applications of John Kutyla and Harry Chanowitz. However, the use of the apparatus disclosed in the Chanowitz application offers a number of manufacturing advantages, and the formation of the depressions 20 and 22 is described with reference to the apparatus and techniques disclosed in this application. In general, this apparatus includes a pair of spaced torch means 30 and 32 between which the sealed switch 10 is disposed with the area to receive the depression 20 generally aligned with the flame from the torch 3t) and with the area to receive the depression 22 aligned with the flame from the torch 32. The flames of the torches 30 and 32 and the period in which these flames are allowed to impinge on the glass of the housing 12 are so adjusted as to provide sufficient heat to soften the glass of the housing in those areas in which the depressions 20 and 22 are to be formed without substantially affecting the adjacent areas of the glass.

When the glass becomes sufficiently softened, the pressure of the flame coupled with the partial vacuum within the sealed housing 12 displaces the glass inwardly so that it moves into engagement with the adjacent edges of the uniplanar portions 140 and 160 of the magnetic elements and flows, to a degree, around the engaged edges to form the recesses 20a and 22a in the depressions 20 and 22. The switch 10 is then removed from the dimpling" apparatus so that by cooling in the ambient atmosphere and by conduction through the reeds 14 and 16, the glass in the depressions 20 and 22 becomes solidified. This heating operation is so controlled that the glass of the depressions 20 and 22 is not permitted to flow completely around the edge surfaces of the end portions 14c and 16c of the reeds so as to freeze these reeds in their normal positions. Further, as described in the copending Chano- Witz application, the sealed switches can be preheated to control the pressure differential between the atmosphere and the interior of the housing 12 so as to provide a force that is just sufficient to move the glass of the depressions and 22 into the desired contact with the reeds 14 and 16.

Since the depressions 2t) and 22 are generally disposed at an angle around to the planes of the uniplanar end portions 140 and 160, a portion of the force of the moving glass engaging the reeds 14 and 16 is applied in a direction transverse to its length in which the reeds are not capable of being deflected. This reduces the value of the component of force applied perpendicular to the planes of the end portions 140 and 16c to such an extent that these end portions are not deflected inwardly toward each other to reduce the gap 18. Thus, the practice of the novel method embodying the present invention provides damping means for the reeds 14 and 16 without producing a change in the preset and previously checked operating characteristics of the switch 10. Because the present method does not cause displacement of the end portions 14c and 160 of the reeds, it is no longer necessary to select switches 10 for dimpling operations that present operating sensitivities or characteristics high in the acceptable range, and its is possible to use switches for dimpling without SCICCtlOl'ltOI regard to the operate sensitivities.

Although the method of making the sealed switch 10 described above can be so performed as to prevent any appreciable displacement of the reeds 14 and 16 or any displacement thereof resulting in a change in the operating characteristic of the switch 10, it is also possible to provide a small and controlled displacement of the reeds that is desirable in some applications. More specifically, it has been determined that it is possible to deflect each of the end portions 140 and 160 a very small amount with the softened glass to reduce the gap 18 to a value some what below the normal value of .010 inch. When the glass of the depressions 20 and 22 solidifies, the slightly deflected positions of the magnetic elements 14 and 16 causes a pretensioning or stressing of these elements against the depressions 20 and 22 to insure their continuous contact with the depressions. This aids in preventing movement of the reeds 14 and 16 in the normal position due to shock or impacts. Because of the force required to overcome the pretensioning, the slight reduc tion in the gap, on the order of .001 or .002 inch, does not materially reduce the operate sensitivity.

The method of the present invention also possesses the further advantage that switches presenting an acceptable amount of eccentnicity between the reeds 14 and 16 and the envelope or housing 12 can be used in the dimpling operation as contrasted with prior methods in which attempts to form depressions in eccentric switches frequently resulted in unacceptable switches. In the prior method shown, for instance, in the copending Chanowitz application, the switch 10, and more particularly, the .housing 12 thereof is located relative to the torch means 3%) and 32 by locating means engaging the planar faces of one or the other of the terminal portions 14!) or 16b of the magnetic reeds 14 and .16. These reeds are inclined relative to the elongated body 12 of the switch 10 to provide the space forming the gap 18 between the overlapped inner ends 140 and 16c thereof. This inclination of the portions 14b and 16b prevents precise location of the body 12 of the switch relative to the torches 30 and 32. In those instances in which the housing 12 is not concentrically arranged with respect to the magnetic reeds 14 d and 16 in a direction perpendicular to the uniplanar end portions and 160, an uneven application of heat in the area of the housing 12 to be softened results in improper formation of the depressions 2t) and 22 or changes in the gap 18.

In the present invention in which the depressions 20 and 22 are formed offset from the overlapped end portions 14c and 160, the jigs or fixtures provided in the assembling apparatus locate the switch 16 with respect to the narrow or edge surface of the portions 14b and 16b which are both rigid and maintained in closely controlled positions during the manufacture of the switch 10. Thus, if the reeds 14 and 16 are eccentrically disposed with respect to the housing 12 along a line connecting the torches 30 and 32 in FIG. 2,. the housing 12 is automatically located closer to or farther away from the torches 30 and 32 in accordance with the nature of the eccentricity to provide an automatic compensation therefor.

As an example, if the switch eccentricity is such that the reeds 14 and 16 are positioned closer to the area of the envelope 12 in which the depression 20 is to be formed, the torch 30 will be positioned further away from this area than in a concentrically formed switch. Similarly, the glass of the envelope 12 in which the depression 22 is to be formed will be spaced further from the reed 16c and closer to the torch 32. This means that the glass of the depression 20 will receive less heat and flame pressure to form a smaller depression 20 that is adequate to reach and engage the more closely adjacent reed 14, whereas the greater heat applied to the glass forming the depression 22 and the corresponding greater flame pressure produce a larger depression 22 for engaging the more remote reed 16. In this manner, even eccentrically formed switches 10 can be provided with the damping depressions 20 and 22 without altering the operating characterist'ics of the switch.

Referring now more specifically to FIG. 5 of the drawrings, therein is shown a sealed switch construction 50 which embodies the present invention and an apparatus for carrying out an improved method of manufacturing this switch. The switch 50 is substantially identical to the switch 10 and includes the elongated dielectric glass housing 12 in which are sealed the magnetic elements 14 and 16 with their inner ends 14c and 16c disposed in a normally spaced and overlapped relation to define the gap 18. However, the overlapped end portions 14c and are not rectangular in section although providing a generally rectangular configuration with; rounded edge surfaces 14a and 16:1.

The sealed magnetic switch 50 includes a pair of damping depressions or projections 52 and 54 which engage not opposite edges of the overlapped portions 14c and 16c as in the switch 10, but adjacent edge portions 14d and 16a of the overlapped ends 140 and 160, respectively. The damping means 52 and 54 includes recesses for engaging the edges of the end portions 14c and 16c, but these recesses are not L-shaped as are the recesses 26a and 22a because of the different configurations of the engaged edge surfaces. The use of slightly rounded edges on the inner ends 140 and Ida of the magnetic elements 14 and 16 together with the corresponding configuration of the recesses in the projections 52 and 54 prevents the possibility that any drag will be applied to the reeds 14 and 16 as they are moved into engagement by the application of a magnetic field. The frictional engagement of the vertical side walls of the end portions 14c and 160 in the switch 119 with the adjacent walls of the recesses 21111 and 22a sometimes results in a force tending to retard closing movement of the magnetic elements 14 and 16 which is avoided by the rounded edges of the elements 14c and 160 in the switch 50. The engagement of the magnetic elements 14 and 16 along adjacent edges of the end portions 140 and 16c, although spaced longitudinally from each other along the housing 12, has been determined to provide adequate damping of the magnetic elements 14 and 16 upon release of the switch 50.

The damping depressions or projections 52 and 54 of the housing 12 of the sealed switch 50 are formed in substantially the same manner as the depressions 20 and 22 in the sealed switch 10. However, the apparatus for producing the dimpled switch 56' includes a pair of torch means 56 and 58 which are disposed generally on the same side of the housing 12 of the switch 1) in positions providing a flame directed substantially at 45 to the planes of the end portions 14c and 16c of the magnetic elements 14 and 16. In other words, the torches 56 and 58 are disposed at positions spaced 45 on opposite sides of a plane passing through the gap 18 parallel to the uniplanar end portions 140 and 160. Thus, the depressions 52 and 54 and the torch means 56 and 58 are spaced angularly from each other about the periphery of the housing 12 around 90.

The torch means 56 and 58 are disposed in general alignment with the areas of the housing 12 in which the depressions or projections 52 and 54 are to be formed, and thus, are spaced longitudinally from each other along the length of the housing 12 of the switch 50. This arrangement of the torches 56 and 58 on the same side of the housing 12 in longitudinally spaced positions avoids the problem presented in apparatus of the type illustrated in FIG. 2 in which the flames of the torches 3G and 32, although spaced from each other along the longitudinal axis of the housing 12, are directed substantially at each other. When a switch 16 is not disposed between the torch means 30 and 32, there is a tendency for the flames from these torches to impinge on each other with the resultant difliculty in maintaining the heating equipment.

When the damping projections or depressions 52 and 54 are to be formed in the housing 12, the switch 50 is placed in a positioning or aligning fixture similar to that shown in the copending Chanowitz application which, however, positions the switch 59 with reference to the edge surfaces 14b and 16b of the magnetic elements 14 and 16 in the same manner as in the switch 10. The flames from the torches 56 and 58 are allowed to heat the aligned portions of the glass of the housing 12 for a period of time sufficient for the pressure of the flames and the partial vacuum within the sealed housing 12 to move the softened portion of the glass into engagement with the edges of the overlapped end portions 140 and 16c. The heating is terminated, and the softened glass is allowed to solidify with the depressions 5?. and 5'4 engaging the end portions 140 and 16c. If desired, this heating can be such as to cause a small amount of inward deflection of the end portions 140 and 160 to provide a slight pretensioning in the manner described above. Since the switch 5% is located relative to the torches 56 and 58 by using the edge surfaces of one or both of the terminal portions 14b or 16b of the magnetic elements 14 and 16, the two depressions 52b and 54b are made either of greater or lesser height in those switches in which the magnetic elements 14 and 16 are not concentrically disposed relative to the housing 12 so as to provide automatic compensation for the eccentric switches 50 in the manner described above. In other words, the glass forming the depressions 52 and 54 receives a greater or lesser quantity of heat and flame pressure in dependence on whether the elements 14 and 16 are disposed closer to or spaced farther from the walls of the housing 12 engaged by the flames of the torches 56 and 58.

Although the present invention has been described with reference to a number of illustrative embodiments thereof, it should be understood that numerous other modifications and embodiments can be devised by those skilled in the art that will fall within the spirit and scope of the principles of this invention.

What is claimed and desired to be secured by Letters Patent of the United States is:

1. A sealed magnetic switch comprising an elongated dielectric housing, a pair of magnetic elements sealed in opposite ends of the housing and having generally parallel inner end portions disposed in a spaced and overlapped relation, the inner end portions being generally uniplanar and formed by two spaced planar surfaces of substantial area joined along their edges by side Walls of substantially smaller area, and a pair of projections in the housing each engaging only one edge portion of one of the inner end portions to provide means for damping movement of the magnetic elements, each of the projections providing a recess at its inner end for receiving the engaged end portion so that the projection engages the one side wall forming the engaged edge portion over an appreciable part of its transverse dimension and engages the planar surface forming the engaged edge portion over a small part of its transverse dimension.

2. The sealed magnetic switch set forth in claim 1 in which the edge portions which are individually engaged by the two projections are located on opposite sides of the two inner end portions.

3. The sealed magnetic switch set forth in claim 1 in which the edge portions which are individually engaged by the two projections are located on the same side of the two inner end portions.

4. The sealed magnetic switch set forth in claim 1 in which the projections extend generally at an angle of 45 with respect to the planes of the engaged end portions.

5. The sealed magnetic switch set forth in claim 1 in which the spaced and overlapped inner end portions define a gap of a given dimension measured perpendicular to the planes of the uniplanar inner end portions when the inner end portions are not stressed, said projections projecting inwardly a distance great enough to deflect the engaged inner end portions to slightly reduce the given dimension of the gap so that the engaged inner end portions are stressed to be resiliently biased against the projections.

References Cited by the Examiner UNITED STATES PATENTS 2,457,218 12/1948 Ferrell -55 2,535,400 12/1950 Ellwood 200l04 3,056,869 10/1962 Dal Bianco et al 200-87 BERNARD A. GILHEANY, Primary Examiner.

ROBERT K, SCHAEFER, Examiner. 

1. A SEALED MAGNETIC SWITCH COMPRISING AN ELONGATED DIELECTRIC HOUSING, A PAIR OF MAGNETIC ELEMENTS SEALED IN OPPOSITE ENDS OF THE HOUSING AND HAVING GENERALLY PARALLEL INNER END PORTIONS DISPOSED IN A SPACED AND OVERLAPPED RELATION, THE INNER END PORTIONS BEING GENERALLY UNIPLANAR AND FORMED BY TWO SPACED PLANAR SURFACES OF SUBSTANTIAL AREA JOINED ALONG THEIR EDGES BY SIDE WALLS OF SUBSTANTIALLY SMALLER AREA, AND A PAIR OF PROJECTIONS IN THE HOUSING EACH ENGAGING ONLY ONE EDGE PORTION OF ONE OF THE INNER END PORTIONS TO PROVIDE MEANS FOR DAMPING MOVEMENT OF THE MAGNETIC ELEMENTS, EACH OF THE PROJECTIONS PROVIDING A RECESS AT ITS INNER END FOR RECEIVING THE ENGAGED END PORTION SO THAT THE PROJECTION ENGAGES THE ONE SIDE WALL FORMING THE ENGAGED EDGE PORTION OVER AN APPRECIABLE PART OF ITS TRANSVERSE DIMENSION AND ENGAGES THE PLANAR SURFACE FORMING THE ENGAGED EDGE PORTION OVER A SMALL PART OF ITS TRANSVERSE DIMENSION. 